I'm using the latest bazzite version with KDE installed by Legion Go ISO from main website. Rumble doesn't work in gaming mode, but it's enabled in controller settings
Displays info about all gamepads connected to your computer. Check buttons, joystick axes, drift, and more. Works with all controllers and joysticks in a modern browser.
because steam does not capture the controller or soemthing by default, so rumble wont work. It will activate if you go to advanced calibration settings which sets the leds